mobile SDK

iOS feature flags

The iOS SDK is a client SDK for iOS, macOS, tvOS and watchOS. It asks Featureflow for values already evaluated for one user. It does not download your rules. Ship a client key (sdk-js-env-…), never a server key. Requires iOS 13+, Swift 5.9+, and the license in the docs is MIT.

iOS docs · GitHub · featureflow-ios-sdk

Set it up with your coding agent

Paste this into Claude Code, Cursor or any coding agent. It installs the iOS SDK, creates the client and evaluates your first flag.

Or set it up by hand

Install

.package(url: "https://github.com/featureflow/featureflow-ios-sdk.git", from: "0.2.0")

Initialise

import Featureflow

let user = FeatureflowUser.Builder("user-123")
    .withAttribute("tier", "gold")
    .withAttributes("roles", ["beta"])
    .build()

let featureflow = await FeatureflowClient.initialize(
    apiKey: "sdk-js-env-YOUR_KEY",
    user: user
)

Evaluate a flag

if featureflow.evaluate("new-checkout").isOn() {
    // the new checkout
} else {
    // the old one
}

Kill switch

Branch on evaluate("new-checkout").isOn(). Set FeatureflowConfig.defaultVariants for the variant to serve before the first fetch and when offline. Anything unlisted is off. For a kill switch whose safe path is on, set that default explicitly. initialize never throws. If Featureflow is unreachable it uses the on-disk cache, then your defaults.

The operational side is the kill switch. Turning the flag off does not require a redeploy.

Gradual rollout

Percentage rollouts bucket on the user id. The docs say an id that changes per launch turns a user rollout into a session rollout. Omit the user and the SDK generates an anonymous id and persists it. Do not delete a flag a shipped build still reads. Archive it instead.

See progressive rollout for the dashboard control. Release pipelines and approval workflows, if the change itself needs a review, are on the Business plan at $399 a month. That price is on the pricing page.

Targeting

FeatureflowUser.Builder(id).withAttribute and withAttributes attach strings, numbers, booleans, dates or arrays. withSessionAttribute is used for the evaluation and is not persisted. await featureflow.updateUser(loggedInUser) on login and logout. JSON config is jsonValue(as:) and returns nil when the variant has none, so keep a fallback. track("purchase", value: 49.95) records a goal.

Frequently asked questions

Other SDKs

• All SDKs
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